Bonding and interfacial reaction between Ni foil and n-type PbTe thermoelectric materials for thermoelectric module applications

Integration of next generation thermoelectric materials in thermoelectric modules requires a novel or alternative approach for mating the brittle semiconducting thermoelectric materials and the ductile metal interconnects. In this study, pure Ni foil was directly bonded to PbTe-based thermoelectric materials using a rapid hot-press. The materials were sintered at 600 and 650 °C, under a pressure of 40 MPa and for various holding times. The resulting interfacial microstructures of the Ni/PbTe joints were investigated. Additionally, the distributions of elements and the phases formed at the Ni/PbTe interface were analyzed. The β_2 phase (Ni_(3±x) Te_2, 38.8–41 at.% Te) was identified at the Ni/PbTe joints bonded at both 600 and 650 °C. A ternary phase with approximate composition Ni_5Pb_2Te_3 was found at the Ni/PbTe joints bonded at 650 °C. Additionally, the PbTe(Ni) phase was observed along the Ni grain boundaries for both bonding temperatures. Thermodynamics calculation results indicate that only the β_2 phase can be formed at the Ni/PbTe interface at 900 K among the binary nickel tellurides.